Un essai de production et de transformation de lait de dromadaire en Tunisie

Dans le Nord tunisien, cinq dromadaires femelles disposant chacune de 4 kg de son de blé par jour et de paille d'avoine à volonté ont produit en 305 jours de lactation une moyenne de 1 860 l (entre 915 et 3 355 l). Différents fromages ont été fabriqués à partir de ce lait composé de 108 g de matière sèche et de 28 g de matière grasse par litre. Des rendements frais et secs de 11,7 p. 100 et 4,9 p. 100 ont été respectivement obtenus avec un taux de récupération de la matière grasse de 64 p. 100. Ces résultats sont comparés à ceux obtenus avec du lait de vache

Evaluation of European Land Data Assimilation System (ELDAS) products using in site observations

Three land-surface models with land-data assimilation scheme (DA) were evaluated for one growing season using in situ observations obtained across Europe. To avoid drifts in the land-surface state in the models, soil moisture corrections are derived from errors in screen-level atmospheric quantities. With the in situ data it is assessed whether these land-surface schemes produce adequate results regarding the annual range of the soil water content, the monthly mean soil moisture content in the root zone and evaporative fraction (the ratio of evapotranspiration to energy available at the surface). DA considerably reduced bias in net precipitation, while slightly reducing RMSE as well. Evaporative fraction was improved in dry conditions but was hardly affected in moist conditions. The amplitude of soil moisture variations tended to be underestimated. The impact of improved land-surface properties like Leaf Area Index, water holding capacity and rooting depth may be as large as corrections of the DA systems. Because soil moisture memorizes errors in the hydrological cycle of the models, DA will remain necessary in forecast mode. Model improvements should be balanced against improvements of DA per se. Model bias appearing from persistent analysis increments arising from DA systems should be addressed by model improvement

Analysis of Simulated Output Characteristics of Gas Sensor Based on Graphene Nanoribbon

This work presents simulated output characteristics of gas sensor transistors based on graphene nanoribbon (GNRFET). The device studied in this work is a new generation of gas sensing devices, which are easy to use, ultracompact, ultrasensitive, and highly selective. We will explain how the exposure to the gas changes the conductivity of graphene nanoribbon. The equations of the GNRFET gas sensor model include the Poisson equation in the weak nonlocality approximation with proposed sensing parameters. As we have developed this model as a platform for a gas detection sensor, we will analyze the current-voltage characteristics after exposure of the GNRFET nanosensor device to NH3 gas. A sensitivity of nearly 2.7% was indicated in our sensor device after exposure of 1 ppm of NH3. The given results make GNRFET the right candidate for use in gas sensing/measuring appliances. Thus, we will investigate the effect of the channel length on the ON- and OFF-current

Environnement humain de l'érosion

Le but de cette étude est d'analyser l'impact des travaux anti-érosifs sur le commportement hydrologique, en termes de crues et de transport solide, de micro-bassins versants expérimentaux dans la zone semi-aride de Tunisie centrale au cours de six campagnes de mesures (avant déménagement et après déménagement). Le traitement de données observées durant la période 1978-1993, nous a permis d'aboutir aux résultats suivants : du point de vue ruisellement, les micro-bassins versants se comportent différemment après la mise en place des travaux anti-érosifs, la forme et les caractéristiques des hydrogrammes de crue ont subi des changements très significatifs. Enfin, on note à la suite des travaux anti-érosifs une nette diminution du transport solide. On présente par ailleurs un essai de modélisation du transport solide. (Résumé d'auteur